The invention relates to shape memory material activated devices, and more particularly, the invention relates to shape memory material activated systems, such as, temperature sensors, drug delivery systems, and the like, which employ a shape memory material activator to create a path through a shell.
Temperature warning devices are used as safety devices for products such as pharmaceuticals, foods, and beverages that are subject to loss of potency or strength, chemical alteration or degradation, spoilage, poisoning, and taste or flavor alteration if they are exposed to high temperature or thawed from a frozen condition. Typically, all products have a restricted temperature range outside of which the product begins to change. Many different types of warning devices exist which warn the consumer if the product has reached or exceed its safe temperature limits. Examples of temperature warning devices are described in U.S. Pat. Nos. 5,735,607; 5,531,180; 5,460,117; 5,335,994; and 4,664,056.
Drug delivery devices, such as transdermal patches or implantable drug delivery systems, are available for delivery of drugs to a patient. These drug delivery devices may be manually activated prior to use, such as by the removal of a peelable liner on a transdermal patch. However, it would be desirable to provide on demand activation of a drug delivery device by use of a shape memory material activator.
It would also be desirable to provide a simple and reliable shape memory activated device for use in a variety of applications.
The present invention relates to the creation of a path through a shell wall with the aid of a shape memory material. The path through the shell wall may release a substance contained in the shell or allow a substance to enter the shell. The devices according to the present invention may be used as temperature sensors or warning devices, drug delivery devices, and the like.
One aspect of the present invention relates to a temperature warning device, drug delivery device, or other device having a shell containing a first substance and an enclosure containing a second substance. Mixing of the substances is achieved by activation of a shape memory material activator. The shape memory material has been deformed in the martensitic state and its As to Af temperature range includes the predetermined temperature which is considered to be the maximum safe temperature of the product. For the temperature warning device, the enclosure is made of either a transparent or opaque material with a transparent window. Once the predetermined temperature has been reached, the shape memory material recovers its shape and in the process applies a stress (tensile, compressive, shear, torsion, or a combination) that results in the creation of a path for the two substances to come in contact. The color of the enclosure fluid changes to indicate this effect and to provide the temperature warning through the transparent window. The path creation is accomplished by the shape memory material by several means such as fracturing, exploding, imploding, puncturing, peeling, tearing, shearing, rupturing, splitting, separating, debonding etc. the shell. The method depends on the type of shell and on how the shape memory material is utilized.
In accordance with one aspect of the present invention, a temperature sensor includes a shell containing a substance capable of providing a visible indication upon release from the shell, and a shape memory material activator for creating a path through the shell to release the substance from the shell in response to exposure to a temperature which is above a maximum safe temperature.
In accordance with an additional aspect of the present invention, a shape memory material activated device for opening a shell containing a substance, the device includes a shell containing a substance, and a shape memory material activator configured to create a path through the shell in response to exposure of the shape memory material to a temperature above a predetermined temperature.
In accordance with a further aspect of the invention, a drug delivery system includes a shell containing a drug, and a shape memory material activator for creating a path to deliver the drug from the shell to a patient when a predetermined temperature of the shape memory material activator is achieved.